I fixed this problem by trashing my hosts file.

After Google searching for a different problem, I discovered that Microsoft changed their Windows Update server to use the ad server domain a248.e.akamai.net.

Next, I deleted the corresponding line from my hosts file, and I noticed a small performance increase on my computer, much to my amazement.

Once I trashed the hosts file, everything worked okay.

did you look at the running tasks?
press ctrl alt del and click on task manager.
then click on the processes tab it shows you everything running
and cpu usage. not sure if you did this already. you might find what is doing it in there. good luck

do the task manager thing.. i had a file called evntsrc.exe on my comp and whenever it ran it ran at 99-100% and slowed my comp down to a near halt.. it was a pain in the neck..

even if that isn't the same file that is bugging you, task manager will show you the % that each program is using the comp, so you can easily find which file or program is bringing yours to the max.. just close that prog or delete it, depending on if it is needed or not..